An inverter is an electronic circuit for converting direct current (DC) to alternating current (AC). Inverters are used in a wide range of applications, from small uninterruptible power supplies for a computer to large electric power transport utility applications, and variable speed industrial drives. Inverters are also used to provide a source of AC power from fuel cell or photovoltaic solar cell power supplies. A common application is to power an AC electric motor.
Three-phase is a common type of AC that can be produced by an inverter and used for electric power applications. An important type of three-phase load is an AC electric motor. A three-phase AC electric motor has a simple design, high torque at low RPM, and high efficiency. Three-phase motors are used for pumps, fans, blowers, compressors, electric and diesel-electric locomotives and many other kinds of motor-driven equipment. Three-phase motors are more compact, less expensive, vibrate less, last longer than a single-phase motor of the same power rating, and are subsequently preferred over single-phase for motors above 10 HP (7.5 kW). Hybrid, fuel cell, and electric vehicles often use three-phase motors because their high starting torque can be used to accelerate a vehicle to a useful speed. A three-phase motor can also be used as a generator for regenerative braking.
Hybrid, fuel cell, and electric vehicles generally have a source of DC power. For example, these vehicles may use electric batteries, ultra-capacitors, fuel cells, and fuel powered generators, all producing DC power. Moreover, the different sources will often have different voltages requiring voltage conversion to effectively use their electrical voltages with an inverter. One approach is to use a voltage converter to obtain the various operating voltages.
Voltage converters usually include a capacitor to condition the DC power input to an inverter. This capacitor can be large and expensive. Accordingly, it is desirable to have a system that reduces the size of the input capacitor. Furthermore, other desirable features and characteristics will become apparent from the subsequent detailed description and the appended claims, taken in conjunction with the accompanying drawings and the foregoing technical field and background.